PROJECT SUMMARY This application aims to investigate whether a mechanism used by a virus to block hepatocyte apoptosis can be translated and optimized to block neuronal cell death following injury. Although several signaling cascades responsible for neurodegenerative changes following stroke and related disorders have been well characterized, effective neuroprotective therapies to treat human conditions continue to elude us. Thus, investigations designed to uncover novel neuroprotective strategies, such as those describe here, are potentially of very high significance. Our laboratory is testing the general hypothesis that distinct cell death pathways, triggered by diverse injurious stimuli or composed of unique biochemical signaling cascades, require a set of common conditions to operate optimally. Over the last ten years, we have defined a neuronal pro-apoptotic signaling cascade characterized by a robust enhancement of voltage dependent K+ currents. This phenomenon ensures the completion of cell death programs by providing a venue for the loss of cytoplasmic K+, establishing a permissive environment for protease and nuclease activation. Interfering with the processes responsible for the apoptotic K+ current surge can effectively block neuronal cell death. In mammalian cortical and midbrain neurons, the current surge is mediated by a de novo SNARE-dependent exocytotic insertion of Kv2.1-encoded K+ channels into the cell membrane. Remarkably, a product of the translation and processing of the hepatitis C virus genomic RNA, the non-structural protein 5A (NS5A), was recently shown to effectively interfere with Kv2.1-mediated apoptotic K+ currents in liver cells and inhibit hepatocyte cell death. In preliminary studies we observed that NS5A could also be employed to rescue neurons following injury and that this protein interferes with the neuronal Kv2.1-mediated apoptotic K+ current surge. In this application we intend to (i) investigate the mechanism responsible for NS5A interference with Kv2.1 functional expression, and (ii) define the molecular domains of NS5A necessary for restricting channel function. These latter experiments will establish the minimal NS5A-derived sequences that can be used for the design of novel neuroprotective probes. The overarching goal of our research program is to devise new therapeutic strategies to protect neurons following injury. We are exploring a novel, possibly groundbreaking approach to achieve this goal by constructively harnessing a biological strategy that evolved to block cell death in the liver and translating it towards the generation of novel methods to treat stroke and other forms of neurodegeneration.